Many buildings have vents which provide routes for exchange, ventilation, circulation and/or movement of air through the surfaces (eg. walls and ceilings) of the building. Buildings may have ventilation systems, which take in “fresh” air from outside of the building and expel “stale” air from inside the building. Fresh air may be taken into a building or stale air may be expelled from a building through one or more vents. Some buildings incorporate other systems and/or apparatus, such as air conditioning systems, heating systems and bathroom fans, which use vents to provide routes for the movement of air through building surfaces.
Typically, a vent is associated with a conduit which conveys air towards or away from the vent. A vent provides a vent passageway in fluid communication with its associated conduit to provide a means for air flow through a building surface. Vents may provide a number of additional functions. For example, vents may comprise features for preventing debris from entering their associated conduits or for providing a more aesthetically pleasing terminus for their associated conduits.
There are many vent designs known in the art. For example:                U.S. Pat. No. 6,520,852 (McKee et al.) discloses a vent with a perimeter flange having a nailing means made of a material with a low coefficient of thermal expansion, such as aluminum. The vent further includes a grill structure and a cap. The cap, which is made from dent resistant plastic, is preferably molded to the nailing means;        U.S. Pat. No. 5,6435081 (Klein) describes a vent screen and vent, which include a vent duct, an exterior grill connected to one end of the vent duct, and a vent screen support assembly connected between the vent duct and the exterior grill; and        U.S. Pat. No. 6,682,415 (Vagedes) discloses a replacement dryer vent which includes a typical exterior vent portion and an interior tube portion. The tube portion extends into a building and has an internal diameter that increases toward its innermost edge (i.e. toward the interior of the building), such that the tube portion slips over the existing cylindrical duct already in the wall.        
Vents typically comprise a flange or the like, which allows the vent to be mounted to a building surface using fasteners that project through the flange and into the building surface. Exposed fasteners used for this purpose may make the vent aesthetically unattractive. Exposed fasteners may also be susceptible to oxidation or similar consequences of being exposed to the environment.
Some vents comprise flow adjustment mechanisms. Such mechanisms allow the flow of air through the vent to be controlled. Because of frequent use and the associated wear, flow adjustment mechanisms used in vents often malfunction or break. Accordingly, there is a general desire to provide vents with flow adjustment mechanisms that are robust and relatively immune to breakage. Vents incorporating such robust flow adjustment mechanisms typically require that the flow adjustment mechanisms and their associated components are relatively large to provide the flow adjustment mechanisms with sufficient strength.
One drawback with such robust flow adjustment mechanisms is that the maximum rate of air flow through a vent and its conduit will typically be limited by the cross-sectional area of the conduit and/or the vent. Robust and correspondingly large flow adjustment mechanisms tend to occupy a larger portion of the vent and to impede the flow of air through the vent.
There is a need for vents which have relatively robust and strong flow adjustment mechanisms that do not unnecessarily impede the flow of air through the vent. There is also a need for vents which are attractive looking.